SOX2 and small cell lung carcinoma: CSCs exhibit self‐renewal capabilities and contribute to tumor invasion, metastasis, and recurrence.[5, 6, 7] A CD133‐positive subpopulation has been identified in SCLC, and revealed consistent the capacity for CSCs.[8, 9, 10, 11] Other markers, including ATP binding cassette transporter G2 (ABCG2), CD44, and sex determining region Y box protein 2 (SOX2), have also been associated with CSCs in SCLC.[12, 13, 14] CSCs maintain self‐renewal through both asymmetric and symmetric divisions, which together preserve a dynamic balance in CSC populations.